1. Field of the Invention
The present invention relates to a disk drive device having a fluid dynamic bearing unit and a manufacturing method of the same.
2. Description of the Related Art
Disk drive devices like a hard disk drive often employ a fluid dynamic bearing unit that enables a stable and fast-speed rotation. For example, according to a motor disclosed in JP 2008-275047 A and having a dynamic pressure bearing, a lubricant is applied between a sleeve that is a part of a stator and a shaft that is a part of a rotor. The rotor is supported in a non-contact manner by dynamic pressure generated in the lubricant, enabling a smooth and fast-speed rotation.
Conversely, there is a demand for disk drive devices to further increase the memory capacity. An example technique to cope with such a demand is to increase a recording density.
A gap between a recording/playing head and a disk surface may be reduced to increase the recording density. When such a gap is narrow, however, it becomes difficult for the recording/playing head to precisely trace the track on the disk surface when even a tiny particle sticks to the disk surface, resulting in a read/write error. In the worst case, the recording/playing head is damaged, and the disk drive device breaks down.
One of the causes of such particles is that the lubricant is excessively applied in the fluid dynamic bearing unit, and the excessive lubricant is splashed together with a fast-speed rotation of the fluid dynamic bearing unit. The splashed lubricant diffuses the interior of the disk drive device, and may build up condensation on the disk surface, thereby being deposited thereon. Conversely, when the lubricant applied in the fluid dynamic bearing unit is insufficient, the lubrication operation for the fluid dynamic bearing unit becomes insufficient, resulting in a break-down in the worst case.
That is, it is necessary to manage the lubricant applied in the fluid dynamic bearing unit to be an appropriate amount. JP 2010-262580 A discloses an example method of inspecting an amount of the lubricant applied in the fluid dynamic bearing unit.
The present invention has been made in view of the aforementioned circumstances, and it is an objective of the present invention to provide a disk drive device that facilitates a management of a lubricant applied in the a fluid dynamic bearing unit.